Cleaning some page animations

-> Fix jump when last page gets delted (issue 10908427)
-> Fade out empty screen
-> If the final page is empty, and that is the current page when
   spring loaded mode ends, animate back to the previous page
   and then fade out the final page. Examples: cancel widget
   or shortcut drop on the final page, scroll to final page and
   drop an icon into a the hotseat, etc.

Change-Id: I13438fb0af6555b6f0b511b7aff51b3972431438

src/com/android/launcher3/SmoothPagedView.java

@@ -52,8 +52,6 @@ public abstract class SmoothPagedView extends PagedView {
         }
 
         public float getInterpolation(float t) {
-            // _o(t) = t * t * ((tension + 1) * t + tension)
-            // o(t) = _o(t - 1) + 1
             t -= 1.0f;
             return t * t * ((mTension + 1) * t + mTension) + 1.0f;
         }